1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.imaging.formats.png.chunks; 18 19 import java.io.ByteArrayInputStream; 20 21 import org.apache.commons.imaging.common.BinaryFileParser; 22 23 /** 24 * A PNG image is composed of several chunks. This is the base class for the chunks, 25 * used by the parser. 26 * 27 * @see <a href="https://en.wikipedia.org/wiki/Portable_Network_Graphics#%22Chunks%22_within_the_file>Portable_Network_Graphics</a> 28 */ 29 public class PngChunk extends BinaryFileParser { 30 public final int length; 31 public final int chunkType; 32 public final int crc; 33 private final byte[] bytes; 34 35 private final boolean[] propertyBits; 36 public final boolean ancillary; 37 public final boolean isPrivate; 38 public final boolean reserved; 39 public final boolean safeToCopy; 40 41 /** 42 * Constructor. 43 * @param length chunk length 44 * @param chunkType chunk type 45 * @param crc CRC computed over the chunk type and chunk data (but not the length) 46 * @param bytes chunk data bytes 47 */ 48 public PngChunk(final int length, final int chunkType, final int crc, final byte[] bytes) { 49 this.length = length; 50 this.chunkType = chunkType; 51 this.crc = crc; 52 this.bytes = bytes.clone(); 53 54 propertyBits = new boolean[4]; 55 int shift = 24; 56 for (int i = 0; i < 4; i++) { 57 final int theByte = 0xff & (chunkType >> shift); 58 shift -= 8; 59 final int theMask = 1 << 5; 60 propertyBits[i] = ((theByte & theMask) > 0); 61 } 62 63 ancillary = propertyBits[0]; 64 isPrivate = propertyBits[1]; 65 reserved = propertyBits[2]; 66 safeToCopy = propertyBits[3]; 67 } 68 69 /** 70 * Return a copy of the chunk bytes. 71 * @return the chunk bytes 72 */ 73 public byte[] getBytes() { 74 return bytes.clone(); 75 } 76 77 /** 78 * Return a copy of the chunk property bits. 79 * @return the chunk property bits 80 */ 81 public boolean[] getPropertyBits() { 82 return propertyBits.clone(); 83 } 84 85 /** 86 * Create and return a {@link ByteArrayInputStream} for the chunk bytes. 87 * 88 * <p>The caller is responsible for closing the resource.</p> 89 * 90 * @return a ByteArrayInputStream for the chunk bytes 91 */ 92 protected ByteArrayInputStream getDataStream() { 93 return new ByteArrayInputStream(getBytes()); 94 } 95 96 }